ndarray的每一行中的N个最大值 [英] N largest values in each row of ndarray

问题描述

我有一个ndarray，其中每一行都是一个单独的直方图.对于每一行，我希望找到前N个值.

I have an ndarray where each row is a separate histogram. For each row, I wish to find the top N values.

我知道全局N个顶级值的解决方案(

I am aware of a solution for the global top N values (A fast way to find the largest N elements in an numpy array), but I don't see how to get the top N for each row.

我可以遍历每一行并应用一维解决方案，但是我不应该能够通过numpy广播做到这一点吗?

I could iterate over each row and apply the 1D solution, but shouldn't I be able to do this with numpy broadcasting?

推荐答案

您可以使用与链接的问题相同的方式使用np.partition:排序已经沿最后一个轴进行了:

You can use np.partition in the same way as the question you linked: the sorting is already along the last axis:

In [2]: array([[ 5,  4,  3,  2,  1],
               [10,  9,  8,  7,  6]])
In [3]: b = np.partition(a, 3)    # top 3 values from each row
In [4]: b[:,-3:]
Out[4]: 
array([[ 3,  4,  5],
       [ 8,  9, 10]])

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